Self-ligating orthodontic bracket assembly

ABSTRACT

A clip for a self-ligating orthodontic bracket assembly has a lifting element between the labial surface of the bracket and the labial portion of the clip that can be rotated to provide a range of adjustability in lifting the labial portion of the clip with respect to the bracket. The lifting element thereby controls the range of motion of the tongue of the clip in its closed position. This limits the forces applied by the clip to an archwire held in the archwire slot of the bracket, and also allows an archwire to slide freely in the slot. A threaded shaft or camming mechanism can be employed as the lifting element.

RELATED APPLICATION

The present application is based on and claims priority to theApplicant's U.S. Provisional Patent Application 61/094,511, entitled“Self-Ligating Orthodontic Bracket Clip,” filed on Sep. 5, 2008.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of orthodontics.More specifically, the present invention discloses a self-ligating clipfor orthodontic brackets.

2. Statement of the Problem

In the standard practice of orthodontics, a wide range of armamentariumis required including wires, springs, bands, brackets and the like.Orthodontic brackets in particular serve as the central conduit fortransferring corrective forces to each individual tooth. Being rigidlyconnected to a tooth, corrective forces are transferred through abracket and thereby to the root of a tooth and then to the supportingbone surrounding the root. The gentle but continuous forces elicit aphysiological response in the supporting bone allowing teeth to slowlyreposition. Orthodontic brackets were developed in the late 1800's, andeven though manufacturing methods and basic configuration have beengreatly improved, the biological functioning of orthodontic bracketsremains unchanged today.

Before proceeding through the history of orthodontic brackets, it isimportant to understand the frame of reference commonly employed indentistry. The term “gingival” refers to a direction toward a patient'sgingiva or gum. The term “occlusal” is the opposite of “gingival” andrefers to a direction toward the occlusal or incisal edge of a tooth(i.e., toward the bite plane between the upper and lower teeth). Theterm “mesial” (or the adjective “mesio”) refers to a direction towardthe mid-line of a patient's dental arch. The “distal” is the opposite of“mesial” and refers to a direction away from the mid-line of a patient'sdental arch. The term “lingual” refers to a direction toward thepatient's tongue. The term “labial,” as applied to the front teeth,refers to a direction away toward the lips. The term “buccal,” asapplied to the bicuspid or molar teeth, refers to a direction toward thecheek. All of these terms are commonly used relative to a specifictooth.

The central feature of an orthodontic bracket is an archwire slot,sometimes referred to as the “slot”. Two parallel walls define the slotfeature, and a slot floor is oriented perpendicular to the walls. Theslot feature is oriented horizontally and extends centrally across thefull mesial-distal width of a bracket. Orthodontists normally placebrackets on all of an orthodontic patient's teeth. The slots open to thelabial or buccal aspects to accept an orthodontic archwire. The archwirespans all of the brackets by engaging the slot of each bracket. Forexample, U.S. Pat. No. 3,504,438 to Wittman et al. discloses orthodonticbrackets with arch slots and an archwire.

It should be understood that it is the relationship between the archslot and the archwire that drives correction of tooth position.Corrective forces are generated by the capturing of an archwire in abracket's slot. Doing so usually requires that the archwire be deflectedfrom its passive arcuate shape, which loads the archwire as a resilientspring. Loading in this manner causes potential energy to be stored inthe archwire. It is the gradual dissipation of the stored energy thatcauses teeth to move into their desired, finished positions andorientations.

Generally, today's orthodontic armamentarium, and in particular,orthodontic brackets benefit from a tradition of constant improvementthat has spanned many decades. In order to contain costs and to makeorthodontic treatment more affordable, orthodontic practices mustconstantly embrace hardware systems and procedures that deliverincreased efficiency. Hardware systems and chairside procedures thatavoid problems, save time and eliminate steps must be embraced in orderto reduce the total amount of treatment time required to treat eachpatient. Today's business environment requires that orthodontists becomesuccessful managers of their practices as a business as well as beingskillful practitioners. One area that exemplifies the tradition ofconstant improvement can be seen in the means with which the orthodonticarchwire is retained in the slots of the brackets. An historical reviewof that follows.

As mentioned earlier, orthodontic brackets were developed in the late1800's. Beginning then and continuing through to roughly the early1980's, archwires were routinely retained in the slots by tying-in thearchwire using ligature wire. During that period, ligature wire was usedin diameters ranging from 0.009 to 0.012 in. Ligature wire is fullyannealed, dead-soft stainless steel exhibiting an ultimate tensilestrength of about 70,000 psi. In the very soft temper and in thosediameters, ligature wire is extremely malleable and can be twisted intoa tight helix. FIG. 7 of U.S. Pat. No. 4,392,494 to Ashby, shows atypical Siamese-type orthodontic bracket with an archwire residing inthe slot. A ligature wire engages the four tie-wings and transverses thebracket, up and over the archwire to tie it in, retaining it tightly inthe slot against the slot floor. After pulling and twisting the ligaturewire as tightly as required, the loose ends of the wire are cut off. Theshort, remaining twisted portion is tucked out of the way, under the tiewings in order to avoid laceration of soft tissue by the sharp ends. Inorder to perform the routine step of changing an archwire, anorthodontist or staff person must carefully repeat the procedure,usually ten times per arch, for a total of twenty times.

Steel ligatures have useful qualities that served orthodontists well.For example, in the case of a highly mal-positioned tooth, a steelligature could first be partially tightened in a manner that avoidedhigh deflection and the tight cinching of the archwire against the slotfloor. At a subsequent appointment, the practitioner had the option ofthen fully tightening the ligature. Such tightening of steel ligaturesallowed the progressive tightening to match desirable tooth movementresponse achieved over several weeks, such as the interval betweenpatient appointments. Had the practitioner fully tightened the ligatureinitially, the patient would likely have experienced significantdiscomfort, and the resulting higher than optimal forces could haveactually resulted in a slower tooth movement rate. Orthodontic patientstreated with steel ligatures were often scheduled for appointments wherethe objective was to simply tighten all of the ligatures. Such atightening served to more aggressively transfer stored energy from thedeflected archwire to the brackets and teeth.

Other common procedures took advantage of the characteristics of steelligatures. For example, in the case of a highly-rotated tooth, thepractitioner had the option of using only the distal pair or mesial pairof tie wings for ligation rather than the conventional use of all fourwings. Selectively using only one pair of tie wings created anadvantageous moment in rotation, which was capable of more effectivelycorrecting a tooth in terms of rotation. Progressively tightening aligature that was placed for rotation was an ideal method for correctingrotated teeth. Steel ligatures, not being of any set length, could takeup the length of tying two wings or the longer route of four wings.Doctors and staff became very accustomed to characteristics of steelligatures and skills associated with ligation facilitated treatmentwell.

In cases with teeth generally well oriented in terms of torque androtation, but requiring translation to a new position, steel ligaturesonce again filled the need well. In those cases, the bracket and itscorresponding tooth would be ligated closely to the archwire, but nottightly. This would permit the tooth to remain under the influence ofthe archwire-archslot relationship while sliding along the archwire inresponse to tractive forces such as an elastic or steel coil spring.During such sliding, the tight but free-sliding ligature around thearchwire would keep the bracket oriented on track, but the steelligature would be configured loosely enough so as to not createexcessive binding or undue friction. Conversely, once the tooth arrivedat its ideal position, the ligature could be fully tightened. Suchtightening served to greatly increase the sliding friction between thearchwire and the bracket. In this way, steel ligatures could be used toallow a bracket to slide freely to its desired position, then oncearriving there, lock it in place. Such a methodology served well such asin closing extraction spaces.

Even though dead-soft stainless steel ligatures served quite well formany years, the shortcomings became more problematic as other areas ofthe orthodontic operatory became modernized. Orthodontists begantreating much larger numbers of patients and steel ligatures did not fitwell into the streamlined needs of a fast-paced orthodontic practice.The amount of time required to change an archwire became excessivecompared to other advancements. After all, steel ligatures requirespecial instruments, and tying an archwire to each tooth is timeconsuming. Further, if each ligature is not placed with care and not cutand tucked properly, the patient's tongue, lips or cheeks can bepainfully pierced. Even though steel ligatures are still used today forcertain treatment situations, they have by and large been supplanted byelastomeric ligatures.

For example, U.S. Pat. No. 6,935,858 (Cleary) shows a typicalorthodontic case with the archwire retained with elastomeric ligatures.Like steel ligatures, elastomeric O-rings are placed to hold thearchwire fully seated in the bracket slots. Elastomeric ligatures arenon-metallic and are injection molded from biocompatible, low-durometerurethane resins. Orthodontic manufacturers typically offer a family ofelastomeric products. Central to such product lines are the ligatures,which can take on any combination of cross-sectional diameter andtoroidal diameter required to fit a range of narrow-to-wide brackets.The man-made elastomeric resins used are generally slightlystiffer/harder than the familiar natural latex “rubber bands” used inorthodontics.

Elastomeric ligatures are typically molded integrally with a carrier andeach ligature is connected to the carrier by a thin runner or sprue.Once the ligature is hooked over one wing of a bracket, the practitionercan fail the sprue by pulling the carrier away. Elastomeric ligaturesare also commercially available individually, along with special placinginstruments. As described, commercial sources of ligatures typicallyoffer a family of elastomeric products molded from the same elastomer.U.S. Pat. No. 5,461,133 (Hammar et al.) discloses some of the othertypes of orthodontic products typically offered along with elastomericligatures, including chains and rotation wedges. Elastomeric urethanematerials are commercially available in many configurations and sizes aswell as a wide array of colors, including metal flake andglow-in-the-dark versions. Such offerings allow orthodontic patients theoption of self-expression, which is thought to increase the patient'scooperation with treatment objectives.

The use of small elastomeric ligatures bypasses the steps of twisting,cutting and tucking as is required when using steel ligatures. Eachelastomeric ligature is initially caught by one of the bracket's tiewings and then stretched over the other tie wings. No additional stepsare required to ligate-in the archwire.

Compared to steel ligatures, elastomeric ligatures do not have quite asmuch adjustability and versatility. For example, steel ligatures weredescribed earlier as allowing a close, but still sliding relationshipbetween a bracket and an archwire for cases where teeth must be bodilytranslated along an archwire. Being stretched in place between the tiewings and over the archwire, elastomeric ligatures are always in tensionand therefore continuously urging the archwire against the slot floor.Such constant working of an elastomeric ligature serves well forrotating and torqueing teeth, but such forces are not as desirable whenlow friction and sliding translation is needed. In most treatmentsituations elastomeric ligatures cannot be held off, and do not allowthe option of progressive tightening, and cannot be adjusted in any way.

In spite of the merits of steel versus elastomeric ligatures, it is theelastomeric version that has been adopted as today's default standard bythe orthodontic profession due to efficiency and speed. Orthodonticstaff can change-out an archwire much more quickly compared to the timerequired using steel ligatures.

Further advancements in the orthodontic armamentarium have resulted inthe self-ligating bracket. Such brackets are designed with newerfeatures that eliminate the need for any sort of ligature all-together.The first successfully functioning self-ligating bracket was developedby Ford, and was disclosed in 1935 through U.S. Pat. No. 2,011,575.Ford's invention disclosed a bobbin, that when rotated clockwise alignedwith other structures allowing an archwire to drop into the slot, butafter rotating the bobbin counter-clockwise, the wire is retained. Eventhough Ford's self-ligating bracket (known as the “Ford lock”) wascommercialized, it did not see widespread popularity. This was likelybecause today's impetus for speed and efficiency was not as critical inFord's day.

The first self-ligating bracket to achieve widespread commercial successwas developed by a Canadian orthodontist, G. H. Hanson. Hanson'sdevelopment was disclosed in U.S. Pat. No. 4,492,573 issued in 1985.Improvements thereto have been disclosed by other patents to Hanson,such as U.S. Pat. No. 5,586,882. Appropriately, Hanson's bracket designis marketed as the “Speed Bracket” as it is known today. The SpeedBracket is very popular with orthodontists world-wide because it furtherreduces the time required to accomplish the task of changing-out anarchwire. The Speed Bracket has an occlusal-gingivally sliding clip.With the clip positioned occlusally, the bracket is considered to be inthe open configuration to accept an archwire. With the clip positionedgingivally, the bracket is in its closed configuration to retain anarchwire. Certain features serve to bias the clip in the open or closedpositions.

As a category, self-ligating brackets have become an important adjunctto today's armamentarium. The designs offered by orthodonticmanufacturers have advanced, overcoming the early problems such astartar build-up blocking the smooth sliding of clips, clips that wouldnot stay open or stay closed, clips that could become loose in themouth, and the increased bulk and height of self-ligating bracketscompared to conventional brackets.

When considering the entire category of self-ligating brackets, they canbe further classified into groups based on the mechanical means forachieving ligation. For example, U.S. Pat. No. 4,712,999 to Rosenbergdescribes a self-ligating bracket with a cover plate that resilientlyengages a corresponding cylindrical section of the bracket. Rosenberg'sclip is a separate part, and hinges open and closed once in position. Animprovement over Rosenberg is exemplified by a living hinge. Forexample, U.S. Pat. Nos. 6,733,286, 6,932,597, 6,960,080 and manysubsequent patents to Abels et al. disclose a ligation cover integrallyattached to the base of the bracket as one piece that moves between anopen and closed position. Yet other innovative means for self-ligationutilize a true fixed hinge for the clip. Even though depicted as anadjunct to lingual brackets, U.S. Pat. No. 6,485,299 (Wildman) disclosessuch a hinging clip. U.S. Pat. No. 6,984,127 to Ming discloses aself-ligating bracket based on a resilient latch that can retain anarchwire once an archwire is forced into the latch.

As can be appreciated, many inventors have contributed improvements tothe field of self-ligating brackets and today there are multiplecategories of such brackets, each delineated by the specific means usedfor securing the archwire in the slot. The present invention is directedto one of these categories of self-ligating brackets. First, to describethe category:

One example of the relevant category of self-ligating brackets is taughtby U.S. Pat. No. 6,071,119 (Christoff et al.). This bracket 20 consistsof a rigid bracket body through which passes a mesial-distal extendingarch slot 30 shown with an archwire 40a residing in the slot. Aone-piece movable latch 32 has a labial portion 34a and a slidingportion 36a. The bracket body 24 includes a retentive lip 44a and a stop46a. The movable latch typical of this category of self-ligatingbrackets is usually formed from spring-temper metal and as such it isbiased inwardly, toward the arch slot, serving to actively restrain thearchwire from escaping from the slot. Such clips may be formed from AISItype 410 stainless steel or 17-7 ph, a stainless alloy. Once formed,sliding clips can be heat treated to a near spring temper and as such,the force level required to deflect the labial portion outward can besignificant. As such, the labial portion of the latch can be consideredas “active” in that with sufficient labially or buccally-directed force,it can flex outward away from the archwire slot floor to the extent thatit is restricted from further outward flexing by a retentive lip feature44a of the bracket body according to Christoff et al.

FIG. 9 of U.S. Pat. No. 7,104,791 to Hanson similarly shows a movablelatch moved to its closed position. The movable latch is configuredsimilarly to the invention of Christoff et al., having features thatlimit the range of lingual-labial or lingual-buccal flexing of thelabial portion, and an inward or lingual spring bias of the labialportion of the latch.

U.S. Pat. No. 7,186,114 to Navarro et al. shows yet another movablelatch in a closed position (FIG. 4a) and in an open position (FIG. 4c).FIG. 4a depicts the archwire-retaining portion of the movable latch 38positioned in its lingual-most position, limited from further lingualmovement by the edge of the recess 48. As can be appreciated, shouldtreatment forces act on the archwire to lift the archwire out of itsslot 28, the archwire will be urged back into a seated position in theslot due to the lingual bias and resilience typically observed in suchsliding latches used with self-ligating brackets of this category.However, if the forces acting to lift the archwire exceed the resilienceof the labial portion of the latch, the latch can open only to the otherend of its range as defined by the lip of the recess 48. The latchflexure-limiting function of the recess 48 is substantially identical tothe retentive lip 44a of Christoff et al.

U.S. Pat. No. 7,214,057 to Voudouris shows yet another self-ligatingbracket with a sliding latch. Of importance when considering the presentinvention, the reader should note the wide tongue portion of the cliplocated generally above numeral 94 in FIG. 11 of the Voudouris patent.It is important to visualize the tongue portion as engaging the samesort of retentive lip functioning as feature 44a and 46a shown byChristoff et al.

The present invention can be viewed as an improved movable latch of thesame general type as those disclosed by these prior art patents. To bestdescribe and illustrate the benefits and advantages of the presentinvention, FIGS. 1-7 show a consolidation of the sliding latch-typefeatures from these prior art patents into a hypothetical compositeconfiguration. In particular, FIG. 1. shows a moving latch 10 that is acomposite of the features of the clips of the prior art patentsdiscussed above. For the purposes of this disclosure, the terms “clip”and “latch” are used interchangeably.

FIG. 2 shows the composite sliding latch 10 in place in its closedposition within the body of the composite bracket 20. The tail 16 of thelatch 10 is a disrupted feature, usually formed as a press operationthat serves as a stop for the latch 10. The stop limits sliding of theclip 10 as it reaches its fully open position and prevents the clip 10from becoming dislodged from the bracket 20.

As pointed out earlier, during the manufacture of such brackets 20, thesliding latch 10 is hardened to a near-spring temper and as such, itmaintains a shape that when in position biases the tongue 18 of the clip10, inward or lingually, as shown in FIGS. 2 and 3.

In FIG. 4, the tongue 18 of the clip 10 is acting on a light, roundarchwire 30, urging it lingually, and cinching it against the slot floorformed in the rigid bracket body 20. Such a configuration is useful forcontrolling a pliable, smaller-diameter round wire 30 such as istypically placed by orthodontists early in treatment. The configurationof the tongue 18 in FIG. 4 enables it to push lingually against theround archwire 30. Thus, the tongue 18 of the clip 10 is well positionedto actively capture the archwire 30, and thereby transfer forces fromthe archwire 30 to the root of the tooth.

The meaning of the term “active”, as it applies to movable latches, canbe explained as follows. Earlier, steel ligatures were described and inparticular the practice of progressively tightening steel ligatures withthe steel ligature engaging only one of the two pairs of ligation wingsof a standard orthodontic bracket was described. That practice served asa means for correcting tooth position in terms of rotation. Later, theelastomeric ligatures were described as also being capable of engagingonly one pair of the two pairs of tie wings of a conventional bracket.For self-ligating brackets, rotation correction is instead pursued usingthe “active” qualities of the sliding latch. As can be appreciated, thelingual or inward biasing of the latch's tongue 18 against a smallerround archwire 30 tends to trap such an archwire against the slot 21floor. In cases where the tooth is undesirably rotated, the springresilience of the sliding latch 10 attempts to deflect the archwire 30into an “S” shape as it spans the brackets on adjacent teeth, asillustrated in FIG. 5. By deflecting the archwire 30 in that manner, itloads the archwire 30 to de-rotate the tooth.

During actual treatment situations, the latch's tongue 18 may becomeangled so as to be in a non-parallel relationship to the slot floor.Such a deflection may last for several weeks, but as the tooth slowlyresponds to these forces and de-rotates toward its desired orientation,the tongue slowly returns to its parallel relationship to the slotfloor. It is the constant spring-biasing by the movable latch 10 and itstongue 18 against an archwire 30 that is considered to be the “active”quality. In summary, it is the labial-lingual flexing, along withtwisting as depicted in FIGS. 5 and 6 resulting from constant dynamicinterplay with the archwire 30 that defines an active sliding latch 10.The commercial success of such self-ligating brackets of the type taughtby the prior art is due largely to the effectiveness of theactive-biased sliding latches.

Later in treatment, for final aesthetic positioning of the teeth,orthodontists typically use larger wires exhibiting a stiffer temper.Such wires are sometimes called “finishing wires”. Finishing wiresexhibit a rectangular cross-section profile. One popular example of thedimensions of such wires is 0.021×0.025 in. An example is depicted inFIG. 7. When such wires are seated in the arch slot of a conventionalself-ligating bracket, the tongue of the sliding latch is held up,further away from the slot floor. As such, the lingual or inward biasingof the sliding latch tongue becomes even more aggressive, acting toforce the finishing wire even more forcefully against the slot floor.

Earlier, recess 48 of FIG. 4a of U.S. Pat. No. 7,186,114 (Navarro etal.) was discussed. The recess 48 in Navarro et al. limits the range offlexure of the tongue of the sliding latch. As can be appreciated fromNavarro et al., the tongue portion of the latch may rest on thelingual-most edge of the recess 48 during early treatment when a smallround archwire resides in the arch slot, but the tongue may rest nearthe labial-most edge of the recess 48 near the end of treatment.

The acceptance and wide use of self-ligating brackets represents animportant advancement in orthodontics. There is however one notableshortcoming in spite of the popularity of conventional self-ligatingbrackets. The problem is similar to the lack of adjustability andversatility associated with the elastomeric ligatures described earlier.Both elastomeric ligatures and active sliding latches cannot beregulated or moderated in any way, and as such they are constantlyapplying cinching forces to the archwire. An unavoidable result of suchconstant working is sliding friction between the archwire and atooth/bracket in translation. Excessive friction between a bracket andan archwire is undesirable in orthodontics and some researches believethat even slight friction and hysteresis in the relative movement of thearchwire in the slot can dramatically slow bodily tooth movement. Inresponse to the friction problem, considerable innovation has occurredas low-friction and zero-friction bracket designs have been promulgated.U.S. Pat. No. 5,470,228 to Franseen et al. and U.S. Pat. No. 5,160,261to Peterson disclose various innovative features directed towardreducing such friction. In the orthodontic lexicon, the term “slidingmechanics” applies to the issues associated with friction betweenbrackets and archwires and other areas of orthodontic hardware. It iscommon for orthodontic treatment plans to accommodate the extraction ofteeth for arch development, and subsequently, the serial distalizationof the upper arch. These are examples of treatment phases where teethmust be translated bodily along an archwire and the considerations ofsliding mechanics apply.

In addition to greatly inhibiting tooth translation rate, tight bindingof the bracket to the archwire can also restrict the mobility of atooth, causing it to be positioned in an unnaturally rigid way in itssupporting bone. Such rigidity of course prevents the normal mobility ofthe root of a tooth within the elastic periodontal ligament. Suchrigidity can undesirably impact blood circulation and the generalvitality of the region of bone supporting the tooth. The amount ofmovement of teeth during eating, speaking and so on would surprise mostpeople, who may have the impression that teeth are rigid. Quite to thecontrary, teeth naturally wiggle in position in response to forces. Thesliding friction resulting from the stiff resilience of the latch'stongue acting against the archwire and the additional friction of thearchwire against the arch slot floor can be a significant impediment toa treatment plan and treatment schedule.

Solution to the Problem. These concerns involving sliding mechanics areaddressed by the present invention. The present invention introduces ameans for regulating the aggressiveness of rotational forces not unlikethe adjustment latitude afforded by steel ligatures described earlier.The present invention also allows a free-sliding relationship betweenthe archwire and the bracket. In addition, with the present invention,the active (and friction-inducing) qualities of the labial portion ofthe sliding clip can be selectively restored as required over the courseof treatment by adjusting a rotating lifting mechanism.

SUMMARY OF THE INVENTION

This invention provides a clip for a self-ligating orthodontic bracketassembly having a lifting element between the labial surface of thebracket and the labial portion of the clip that can be rotated toprovide a range of adjustability in lifting the labial portion of theclip with respect to the bracket. The lifting element thereby controlsthe range of motion of the tongue of the clip in its closed position.This limits the rotational forces applied by the clip to an archwireheld in the archwire slot of the bracket, and also allows an archwire toslide freely in the slot. A threaded shaft or camming mechanism can beemployed as the rotating lifting element.

These and other advantages, features, and objects of the presentinvention will be more readily understood in view of the followingdetailed description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more readily understood in conjunction withthe accompanying drawings, in which:

FIG. 1 is a perspective view of a conventional clip 10 for aself-ligating orthodontic bracket.

FIG. 2 is a perspective view of a conventional self-ligating bracket 20and clip 10 in the closed position.

FIG. 3 is a perspective view of a conventional self-ligating bracket 20and clip 10 in the open position.

FIG. 4 is a perspective view of a conventional self-ligating bracket 20and clip 10 in the closed position holding a round archwire 30.

FIG. 5 is a perspective view of a conventional self-ligating bracket 20and clip 10 in the closed position holding an archwire 30 that has beendeflected into an “S” shape by a rotated tooth.

FIG. 6 is a perspective view of the clip 10 corresponding to FIG. 5.

FIG. 7 is a perspective view of a conventional self-ligating bracket 20and clip 10 holding a finishing archwire 35.

FIG. 8 is an exploded perspective view of an embodiment of the presentinvention showing a bracket 20 having a threaded hole 24 to receive athreaded lifting element 14.

FIG. 9 is a perspective view showing the embodiment in FIG. 8 after ithas been assembled.

FIG. 10 is a perspective view of the clip 10.

FIG. 11 is a side cross-sectional view corresponding to FIG. 9 with thelifting element 14 adjusted to raise the tongue 18 of the clip 10 to apassive position.

FIG. 12 is a side cross-sectional view corresponding to FIGS. 9 and 11showing the lifting element 14 fully threaded into the bracket 20,thereby allowing the tongue 18 of the clip 10 to move to an activeposition.

FIG. 13 is a perspective view of another embodiment of a bracket 20having a hole 27 with camming surfaces 29 to actuate a lifting element.

FIG. 14 is a perspective view of a lifting element 17 for use with thecamming surfaces 29 of the bracket 20 in FIG. 13.

FIG. 15 is a perspective view of the lifting element 17 assembled withthe bracket 20.

FIG. 16 is a perspective view of the completed assembly of the clip 10,bracket 20 and lifting element 17.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 8-12 show an embodiment of the present invention that employs athreaded lifting element 14 to adjustably lift the labial portion of theclip 10 from the labial surface of the bracket 20. This, in turn,adjusts the force exerted by the tongue 18 of the clip 10 on an archwire30 in the archwire slot 21. The major components of this embodiment arethe bracket 20, sliding clip 10, and a rotatable lifting element 14.

The bracket 20 is shown in FIG. 8. The base has a conventional base forattachment to a tooth (e.g., by adhesive). An archwire slot 21 extendsin a substantially horizontal, or mesio-distal direction across body ofthe bracket 20 with an open labial aspect to receive an archwire. Thearchwire slot 21 can have a cross-section forming three sides of arectangle, as shown in FIGS. 8, 11 and 12, to better engage an archwirewith a rectangular cross-section. A channel 22 extends through thebracket 20 in an occlusal-gingival direction behind the archwire slot21. The labial surface of the occlusal portion of the bracket 20 has acurved contour to follow the contour of the labial portion of the clip10, as will be discussed below. The bracket 20 also includes a recess 25adjacent to the archwire slot 21 for receiving the tongue 18 of the clip10 in its closed position. The labial surface of the bracket 20 featuresa threaded hole 24 to engage the lifting element 14.

Preferably, the clip 10 is generally J-shaped as shown in theperspective view in FIG. 10. The back of the J forms the lingual aspectof the clip 10 and has dimensions selected to allow the lingual portionof the clip 10 to slide within the channel 22 of the bracket 20 betweenthe clip's open and closed positions. A stop 16 is located at the stemof the J to prevent the clip 10 from becoming dislodged from the bracket20. The labial aspect of the clip 10 can be curved to generally matchthe labial contour of the curved occlusal portion of the bracket 20. Thetongue 18 of the clip 10 is designed to seat in the recess 25 of thebracket 20 when the clip 10 is in the closed position, as shown in FIGS.9, 11 and 12.

The rotatable lifting element 14 has a threaded shaft with an enlargedhead (e.g., a screw or bolt), as shown in FIG. 8. The threads of thelifting element 14 engage the threaded hole 24 in the labial surface ofthe bracket 20. FIG. 9 is a perspective view showing the embodiment inFIG. 8 after it has been assembled. The head of the lifting element 14rests under the lingual surface of the labial portion of a clip 10, andserves to lift the lingual surface of the labial portion of the clip 10away from the labial surface of the bracket 20. The degree of lift iscontrolled by rotating the lifting element 14 clockwise to lower theclip 10 or counter-clockwise to raise the clip 10.

As can be seen in FIG. 9, the head of the lifting element 14 rests underthe curved lingual surface of the labial portion of the clip 10 when theclip 10 is in its closed position. As the lifting element 14 isloosened, the head of the lifting element 14 serves to lift the tongue18 of the clip 10 to an intermediate or passive position in the recess25 in the bracket 20. FIG. 11 is a side cross-sectional viewcorresponding to FIG. 9 with the lifting element 14 adjusted to raisethe tongue 18 of the clip 10 to a passive position. In this passivestate, the tongue 18 is incapable of exerting cinching forces on thearchwire 30. Even though the tongue 18 is poised near the archwire 30 inthe slot 21, no forceful contact occurs except in situations where thetooth is undesirably rotated. Lacking contact due to rotation, thearchwire 30 is allowed to slide freely in the archwire slot 21 of thebracket 20. The deleterious effects described earlier resulting fromholding the tooth rigidly and lack of mobility are thereby avoided.Treatment phases requiring translation of the teeth may be accomplishedwhile still controlling the tooth's orientation and inclination.

Later in treatment as the aesthetic finishing phase approaches, anorthodontist may wish to return the bracket 20 to active functioning. Todo so, the lifting element can be threaded further into the bracket,thereby lowering the tongue 18 of the clip to the active position shownin FIG. 12, so that the tongue 18 exerts resilient force on the archwire30. In this state, the clip 10 functions like any sliding latch ofconventional self-ligating brackets. The tongue 18 of the clip 10delivers exacting forces to the archwire 30, serving to position thetooth in its final ideal position.

Thus, the threaded lifting element 14 can be readily adjusted inward oroutward to achieve any needed balance between passive or activefunctioning of the clip's tongue 18 against an archwire 30. The liftingelement 14 shown in FIGS. 8 and 9, can be adjusted as desired over thecourse of treatment using a jeweler's screwdriver. Alternatively, themeans for adjusting the threaded lifting element 14 can be a hex-socketAllen-type engagement, torqs, hexagonal bolt head, Phillips head, orother standard means.

As can be seen in FIGS. 9 and 10, an elongated slot 15 can be formed inthe clip 10 to allow the adjustment features of the threaded liftingelement 14 to be accessible, and to allow the sliding clip 10 to movebetween its open and closed positions. This slot 15 is envisioned asserving dual functions. For example, the portion of the threaded liftingelement 14 protruding into and above the slot 15 in the clip 10 may alsoserve as a stop, establishing the range of the open and closed positionsof the clip 10. This auxiliary function may eliminate the need fortraditional means for limiting travel of the clip. Further, the threadedlifting element 14 may serve to bias the clip 10 in an open or closedposition.

It should be understood that other mechanisms could substituted in placeof the threaded lifting element 14 in the embodiment depicted in FIGS.7-12. In particular, any of a variety of screw mechanisms could beemployed to lift the lingual surface of the labial portion of the clip10 from the labial surface of the bracket 20.

For example, one alternative shown in FIGS. 13-16 employs a set ofrotational camming surfaces 29 in a radial pattern formed in the labialsurface of the bracket 20 to engage and actuate a lifting element 17that is held between the bracket 20 and the lingual surface of thelabial portion of the clip 10. As shown in FIG. 14, the lifting element17 in this embodiment has a central shaft that seats in a hole 27 in thelabial surface of the bracket 20, and two arms 19 extending outward fromthe shaft. The arms 19 ride on the camming surfaces 29 arranged in aradial pattern about the central hole 27. The camming surfaces 29 causethe lifting element 17 to raise or lower the tongue 18 of the clip 10 asthe lifting element 17 is rotated. FIG. 13 is a perspective view of thebracket 20 showing the hole 27 and camming surfaces 29. The liftingelement 17 can be progressively adjusted over the course of treatment,if desired, by rotating the head of the lifting element 17 with pliersor forceps. The camming surfaces 29 could also be designed so that thelifting element can be rotated between its active and passive positions,but will tend not to remain in an intermediate position.

With either embodiment, the head of the lifting element can have anoblong or elongated shape as shown in FIGS. 15 and 16 to serve as avisual indicator. At a glance, the orthodontist or staff can easilyascertain the bracket's active or passive status from the rotationalposition of the head of the lifting element. The head of the liftingelement 17 can also include a hex-socket Allen-type engagement, torqs,hexagonal bolt head, Phillips head, or other standard means for rotatingthe lifting element 17.

These lifting mechanisms can be generalized to include virtually anytype of screw or rotating camming mechanism that can formed or placedbetween the labial surface of the bracket 20 and lingual surface of thelabial portion of the clip 10. For the purposes of this disclosure, theterm “lifting element” is intended to encompass all such mechanisms.

The above disclosure sets forth a number of embodiments of the presentinvention described in detail with respect to the accompanying drawings.Those skilled in this art will appreciate that various changes,modifications, other structural arrangements, and other embodimentscould be practiced under the teachings of the present invention withoutdeparting from the scope of this invention as set forth in the followingclaims.

1. A self-ligating orthodontic bracket assembly comprising: a brackethaving: (a) an archwire slot extending mesio-distally across the bracketfor receiving an archwire; (b) a channel extending through the bracketin an occlusal-gingival direction; and (c) a labial surface; a cliphaving: (a) a back forming the lingual aspect of the clip, slidingwithin the channel of the bracket between an open position and a closedposition for the clip; (b) a labial portion; and (c) a tongue extendingfrom the labial portion of the clip across the archwire slot when theclip is in the closed position, and being retracted from the archwireslot when the clip is in the open position; and a rotatable liftingelement having a threaded shaft threaded into the labial surface of thebracket adjustably lifting the labial portion of the clip from thelabial surface of the bracket, thereby adjusting the force exerted bythe tongue of the clip on an archwire in the archwire slot.
 2. Theself-ligating orthodontic bracket assembly of claim 1 wherein the clipis substantially J-shaped.
 3. The self-ligating orthodontic bracketassembly of claim 1 wherein the labial portion of the clip is contouredto follow the contour of the labial surface of the bracket.
 4. Theself-ligating orthodontic bracket assembly of claim 1 wherein thelifting element further comprises a head lifting the labial portion ofthe clip.
 5. The self-ligating orthodontic bracket assembly of claim 4wherein the clip further comprises a slot through the labial portion ofthe clip providing access to the head of the lifting element.
 6. Theself-ligating orthodontic bracket assembly of claim 5 wherein the slotthrough the labial portion of the clip has a length selected to limitthe range of travel of the clip between the open and closed positions.7. A self-ligating orthodontic bracket assembly comprising: a brackethaving: (a) an archwire slot extending mesio-distally across the bracketfor receiving an archwire; (b) a channel extending through the bracketin an occlusal-gingival direction; (c) a labial surface; and (d) cammingsurfaces in a radial pattern on the labial surface of the bracket; aclip having: (a) a back forming the lingual aspect of the clip, slidingwithin the channel of the bracket between an open position and a closedposition for the clip; (b) a labial portion; and (c) a tongue extendingfrom the labial portion of the clip across the archwire slot when theclip is in the closed position, and being retracted from the archwireslot when the clip is in the open position; and a lifting elementrotating on the camming surfaces between the clip and the bracket toadjustably lift the labial portion of the clip from the labial surfaceof the bracket and thereby adjust the force exerted by the tongue of theclip on an archwire in the archwire slot.
 8. The self-ligatingorthodontic bracket assembly of claim 7 wherein the lifting elementcomprises a central shaft and at least one arm extending outward fromthe central shaft to slide on a camming surface.
 9. The self-ligatingorthodontic bracket assembly of claim 7 wherein the clip issubstantially J-shaped.
 10. The self-ligating orthodontic bracketassembly of claim 7 wherein the clip further comprises a slot throughthe labial portion of the clip.
 11. The self-ligating orthodonticbracket assembly of claim 10 wherein the slot through the labial portionof the clip has a length selected to limit the range of travel of theclip between the open and closed positions.
 12. The self-ligatingorthodontic bracket assembly of claim 10 wherein the lifting elementfurther comprises a head extending through the slot in the clip.
 13. Theself-ligating orthodontic bracket assembly of claim 7 wherein the headof the lifting element further comprises a visual indicator of thestatus of the clip.
 14. The self-ligating orthodontic bracket assemblyof claim 7 wherein the labial portion of the clip is contoured to followthe contour of the labial surface of the bracket.